• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.237-242
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• 2001

The stochiometric mix of evaporating materials for the CuGaSe$_2$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, CuGaSe$_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were 610$^{\circ}C$ and 450$^{\circ}C$, respectively The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the CuGaSe$_2$ single crystal thin film, we have found that the values of spin orbit splitting Δ So and the crystal field splitting ΔCr were 91 meV and 249.8 meV at 20 K, respectively. From the Photoluminescence measurement on CuGaSe$_2$ single crystal thin film, we observed free excition (Ex) existing only high quality crystal and neutral bound exiciton (D$^{\circ}$,X) having very strong peak intensity. Then, the full-width-at-half-maximum(FWHM) and binding energy 7f neutral acceptor bound excision were 8 meV and 35.2 meV, respectivity. By Haynes rule, an activation energy of impurity was 355.2 meV

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.788-791
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• 2002

Tin doped indium oxide(ITO) films are highly conductive and transparent in the visible region whose property leads to the applications in solar cell, liquid crystal display, thermal heater, and other sensors. This paper investigated ITO films as a transparent conducting films for application of PDP. ITO films were grown on glass substrate by RF magnetron sputtering method. To achieve high transmittance and low resistivity, we examined the various film deposition such as substrate temperature, gas pressure, annealing temperature, and deposition time. We recommend the substrate temperature of $500^{\circ}C$ and post annealing of $200^{\circ}C$ in $O_2$ atmosphere for good conductivity and transmittance. From XRD examination, ITO films showed a preferred(222) orientation. As substrate temperature increased from RT to $500^{\circ}C$, the intensity of the (222) peak increased. The highest peak intensity was observed at a substrate temperature of $500^{\circ}C$. with the optimum growth conditions, ITO films showed resistivity of $1.04{\times}10^{-4}{\Omega}-cm$ and transmittance of 81.2% for a film 300nm thick in the wavelength range of the visible spectrum.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.263-268
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• 2008

Building Integrated PV(BIPV) is one of the best fascinating PV application technologies. To apply PV module in building, various factors should be reflected such as installation position, shading, temperature, and so on. Especially a temperature should be considered, for it affects both electrical efficiency of a PV module and heating/cooling load in a building. This study investigates a semitransparent PV module that is designed as finished material for windows. Therefore it needs to considerate about the optical characteristics of the transparent module. It reports the effect of thermal and optical characteristics of the PV module on generation performance. The study was performed by measuring sun spectrum and luminance through the PV modules and by monitoring the temperature and experiment. The results showed that 1 degree temperature rise reduced about 0.48% of output power.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.4
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• pp.139-143
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• 2005

For application of carbon nano-tube (CNT) as a counter electrode materials of dye-sensitized solar cell (DSSC), the electrochemical behavior of CNT electrode was studied, employing cyclic-voltammetry (C-V) and impedance spectroscopy. Fabrication of CNT-paste and formation of CNT-counter electrode for characteristic measurement have been carried out using ball-milling and doctor blade process, respectively. Unit cell for measurements was assembled using Pt electrode, CNT electrode, and iodine-embedded electrolyte. Field emission-scanning electron microscopy (FE-SEM) was used for structural investigation of CNT powder and electrode. Sheet resistance of electrode was measured with 4-point probe method. Electrochemical properties of electrode, C-V and impedance spectrum, were studied, employing potentiogalvanostat (EG&G 273A) and lock in amplifier (EG&G 5210). As a results, the sheet resistance of CNT electrode is almost similar to that of F-doped SnO2 (FTO) coated glass substrate as approximately 10 ohm/sq. From C-V and impedance spectroscopy measurements, it was found that CNT electrode has high reaction rate and low interface reaction resistance between CNT surface and electrolyte. These results provides that CNT electrode were superior to that of conventional Pt electrode. Particularly, the reaction rate in the CNT electrode is about thrice high than Pt electrode. Therefore. CNT electrode is to be good candidate material for counter electrode in DSSC.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.857-860
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• 2003

Tin doped indium oxide(ITO) and Al doped zinc oxide(ZnO:Al) films, which are widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors, were prepared by using the capacitively coupled DC magnetron sputtering method. The electrical and optical properties of both the ITO and ZnO:Al thin films were investigated as functions of substrate temperature, working gas pressure and deposition time. ITO and ZnO:Al films with the the present experimental conditions of temperature and pressure showed resistivity of $2.36{\times}10^{-4}{\Omega}-cm,\;9.42{\times}10^{-4}{\Omega}-cm$ and transmittance of 86.28%, 90.88% in the wavelength range of the visible spectrum, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.969-972
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• 2004

Al doped Zinc Oxide(ZnO:Al) films, which is widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors, were prepared by using the capacitively coupled DC magnetron sputtering method. In this paper the effect of doping amounts of $Al_2O_3$ on the electrical, optical and morphological properties were investigated experimentally, The results show that the structural and electrical properties of the film are highly affected by the doping. The optimum growth conditions were obtained for films doped with 2 wt% of Al203 which exhibit a resistivity of $8.5{\times}10^{-4}{\Omega}-cm$ associated with a transmittance of 91.7 % for 840 nm in film thickness in the wavelength range of the visible spectrum.

• Ocean and Polar Research
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• v.35 no.4
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• pp.281-290
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• 2013

The vertical structure of sediment temperatures in the tidal flats of Geunso Bay and Seonyu Island in western Korea were measured for more than a year and analyzed. Mean temperature decreased with depth in spring and summer. On the contrary, it increased with depth in fall and winter, faithfully reflecting the seasonal variation resulting from the heating and cooling of the surface sediment. The surface sediment temperatures are shown to be strongly dependent on solar radiation, M2, and M4 tidal components. They are also weakly affected by precipitation. Thermal diffusivity of sediment is estimated at each depth and in each of the four seasons by applying the amplitude equation method. In Geunso Bay, the estimated seasonal-mean values decreased with depth, while they showed little change in Seonyu Island. Depth-averaged thermal diffusivity in Geunso Bay ($1.94 {\times}10^{-7}m^2/s$) was smaller than Seonyu Island ($2.20 {\times}10^{-7}m^2/s$). The variability of thermal diffusivity is shown to corelate with sediment composition and sorting from the grain-size analysis of intertidal sediments in Geunso Bay and Seonyu-do.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2207-2211
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• 2011

Colloidal cadmium telluride (CdTe) quantum dots (QDs) and their nanoparticles have been synthesized by one pot sonochemical reactions under multibubble sonoluminescence (MBSL) conditions, which are quite mild and facile compared to other typical high temperature solution-based methods. For a typical reaction, $CdCl_2$ and tellurium powder with hexadecylamine and trioctylphosphine/trioctylphosphineoxide (TOP/TOPO) as a dispersant were sonicated in toluene solvent at 20 KHz and a power of 220W for 5-40 min at 60 $^{\circ}C$. The sizes of CdTe particles, in a very wide size range from 2 nm-30 ${\mu}m$, were controllable by varying the sonicating and thermal heating conditions. The prepared CdTe QDs show different colors from pale yellow to dark brown and corresponding photoluminescence properties due mainly to the quantum confinement effect. The CdTe nanoparticles of about 20 nm in average were found to have band gap of 1.53 eV, which is the most optimally matched band gap to solar spectrum.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.52.2-52.2
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• 2010

107P/(4015) Wilson-Harrington is one of possible candidates of the dormant or inactive comet nuclei. It was discovered on a photographic plate exposed with the 48-inch Schmidt at Palomar Observatory on 1949 November 19 UT, displaying the faint extended cometary tail. No comet activity has not been after 1949 apparition. Here we present the optical observations of 107P/(4015) Wilson - Harrington during 2009/2010 apparition taken in search of low-level comet activity. Our photometric and spectroscopic data were collected 28 - 86 days after the perihelion passage on 2009 October 22 in a wide range of solar phase angle of 39-68 degree. A disk-integrated phase function was constructed, giving a geometric albedo of 0.055+/-0.012, phase integral of q=0.34, and Bond albedo of A_B=0.019. The photometric property shows profile similar to low albedo asteroids and comet nuclei. Any emission lines were found in our spectrum, giving a flat reflectance similar to low albedo asteroids. Although we could not find any evidence for the comet activity in our photometric and spectroscopic data, we found an upper limit of the fractional active area of 0.001%. We derived the upper limit of the optical depth of the dust trail and tail 7x10^{-10}. We conclude that 107P/(4015)Wilson-Harrington became completely dormant or inactive in 2009/2010 return.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.166.1-166.1
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• 2014

We have controlled the graphene surface in two ways to improve the device performance of optoelectronics based on graphene transparent conductive films. We controlled multilayer graphene (MLG) work function and localized surface plasmon resonance wavelength using a silver nanoparticles formed on graphene surface. Graphene substrates were prepared using a chemical vapor deposition and transfer process. Various size of silver nanoparticles were prepared using a thermal evaporator and post annealing process on graphene surface. Silver nanoparticles were confirmed by using scanning electron microscopy (SEM). Work functions of graphene surface with various sizes of Ag nanoparticles were measured using ultraviolet photoelectron spectroscopy (UPS). The result shows that the work functions of MLG could be controlled from 4.39 eV to 4.55 eV by coating different amounts of silver nanoparticles while minimal changes in the sheet resistance and transmittance. Also the Localized surface plasmon resonance (LSPR) wavelength was investigated according to various sizes of silver nanoparticles. LSPR wavelength was measured using the absorbance spectrum, and we confirmed that the resonance wavelength could be controlled from 396nm to 425nm according to the size of silver nanoparticles on graphene surface. To confirm improvement of the device performance, we fabricated the organic solar cell based on MLG electrode. The results show that the work function and plasmon resonance wavelength could be controlled to improve the performance of optoelectronics device.